1. Field of the invention
The invention concerns secure communications and more particularly communications using a public key encryption/decryption system.
2. Description of the prior art
With the growth of personal computers, the use of electronic (i.e. digital) information transfer has grown rapidly. Electronic mail is an application now widely used in the business community for exchanging all kinds of information, sometimes information of a confidential nature.
To preserve this confidentiality, it is vital that the information passes from the sender to the receiver without any third party being able to interpret the content of the information if the communication is intercepted. Encryption/decryption systems have therefore been developed, in particular so-called public key encryption/decryption systems.
To set up a secure communication between two users by means of a public encryption/decryption system, each user first generates a pair of keys, one being a secret key and the other being a public key. Each user retains their secret key and transmits the public key to the other user by any appropriate means. If the first user decides to transmit secure information to the second user, the first user encrypts that information using the public key of the second user, who alone is able to decrypt it using the second user's own secret key. Conversely, if the second user decides to transmit secure information to the first user, the second user encrypts the information with the public key of the first user, who alone can decrypt it using the first user's own secret key. In this way secure communications can easily be set up between a large number of users who generate their own pair of keys, but there is no means of controlling the expansion of the network of users. This problem can be solved by generating the pairs of user keys at a central location. This solution leads to another problem, however. It is necessary for a user's secret key to be communicated to the user securely, which rules out any form of electronic communication. In practice, the users' secret keys must be transmitted physically to the users, which can become a heavy administrative burden when the number of users is large.
An aim of the invention is to propose a solution to the problem of setting up secure communications between users by means of a public key encryption/decryption system enabling control over the deployment of the network of users and free of the disadvantages mentioned hereinabove.
The invention applies in particular to controlling a network of users within an organization such as an enterprise.